An existing viewing window-based digital holographic display may be used to concentrate a diffraction beam output from a spatial light modulator on a pupil of a user through a convergent optical system so that the user may view a holographically reproduced image.
Such a method may provide the spatial light modulator that is a main component included in the viewing window-based digital holographic display as a commercial liquid crystal display (LCD) panel suitable for a large screen despite a small diffraction angle due to a large pixel pitch. For example, the viewing window-based holographic display may provide a user with a large-screen hologram image with a wide viewing angle using an existing commercial LCD panel in lieu of a high-performance spatial light modulator and by moving a viewing window based on a location of a pupil of the user.
However, the convergent optical system of the digital holographic display that may concentrate a diffraction beam to generate a viewing window may have an optical aberration, and thus a distortion may occur in a holographically reproduced image observed through the viewing window.
Such a distortion may drastically degrade a quality of a stereoscopically reproduced image, and thus using the viewing window-based holographic display as a commercial three-dimensional (3D) stereoscopic video display may not be easy. Further, when using a spatial light modulator having a large screen to provide a large-screen holographic display, a size of an aperture of a convergent optical system may increase as the size of the screen of the spatial light modulator increases. Thus, when using the convergent optical system, a plurality of lens having a large aperture may need to be used, and thus a cost of production may increase and a volume may also increase.